Optical square prism.



. A. KNIG. T if OPTICAL SQUARE PRISM.

APPLICATION FILED JAN.6, 1914.

Patented June 23, 1914. 'a

UNITED STATES PATENT OFFICE.

ALBERT KNIG, OF JENA, GERMANY, ASSIGNOR TO THE FIRM 0F CARL ZEISS, OF JENA, GERMANY.

OPTICAL SQUARE PRISM.

Specification of Letters Patent.

Patented June 23, 1914.

Application filed January 6, 1914. Serial No. 810,567.

To all wlmmit may concern Be it known that I, ALBERT KNIG, a citizen of the German Empire, residing at Jena, Germany, have invented a new and useful Optical Square Prism, of which the following is a specification.

The present invention relates to an optical square prism, which is intended to be placed before or behind an objective, and in which the surface of entrance and the surface of emergence of the rays as also the reflecting surfaces are perpendicular to the same plane, the plane of principal section of the prism. As for a prism destined to be so used the size of the surfaces of entrance and emergence is of especial importance, because this size fixes the amount of light the prism is capable of receiving, the form of these surfaces, on the other hand, is of less importance, such a prism is constructed according to the present invention, when a specially small volume is desired, in such a manner that each of the surfaces of entrance and emergence is, instead of being as usual a square, a rectangle, the longer sides of which are perpendicular to the plane, which is perpendicular to the said surfaces. As in a prism the volume varies directly as that dimension of the surfaces of entrance and emergence, which is perpendicular to the plane of principal section, and as the square of the dimension parallel to the said plane, the volume of a prism of the described form is for a given size of the surfaces of entrance and emergence smaller than that of a prism, in which the said surfaces are of the same size but of square shape.

Vhen it is required with the new form of prism to deflect a ray pencil system by 90, but is at the same time important for the ray pencil system to have the same thickness in the plane of deflection, as in the direction perpendicular 'to the said plane, two prisms, each deflecting the ray passing through it by 90 and each having surfaces of entrance and emergence, each of which is formed as a rectangle having its longer side twice as long as its shorter side, may be combined to form a system in such a manner that each of the surfaces of entrance and emergence of the one prism is parallel to one such surface of the other prism and is directed toward the same side as such surface and that the projection of each pair of such parallel surfaces onto a plane parallel to them is a square. The volume of such a system is then only half as great as that of a single prism, the surfaces of entrance and emergence of which are square and agree each with the square surface of entrance or emergence presented by a pair of such surfaces of the system.

In the annexed drawing: Figure 1 is a perspective view of a prism constructed according to the invention. Figs. 2 and 3 show in elevation and plan respectively a system composed of two prisms according to the invention.

The prism in Fig. 1 is a pentagonal prism for a 90 deflection. The silvered reflecting surfaces are marked a an`d the two rectangular surfaces of entrance and emergence are marked b. The limiting edges c of the surfaces of entrance and emergence, which edges are perpendicular to the plane of principal section of the prism, are longer than the limiting edges l of the said surfaces, which edges are parallel to the said plane.

In the system, Figs. 2 and 3, the two pentagonal prisms e1 and e2, which are of equal size, each deflect by 90 and are cemented onto a plate 0. The reflecting surfaces are again marked a. The surfaces of entrance and emergence in each prism are marked b1 and b2 respectively. The surfaces b1 are parallel to one another and are bot-h turned the same way, the same being the case with the surfaces b2. The limiting edges c of the surfaces of entrance and emergence, which edges are perpendicular to the common plane of principal section of the prisms, are in this example twice the length of the edges d, which are parallel to the said plane. The prism e1 abuts with that edge, with which its surface b2 adjoins the reflecting surface adjacent to it, on that edge of the prism c2, with which the surface b1 of the latter adjoins the reflecting surface adjacent to it. With the direction of rays indicated in the drawing the two surfaces b1 together form a surface of entrance, which agrees with the projection of these two surfaces onto a plane arallel to them, in other words is a square liaving a length of side equal to that of the edges c. Similarly the two surfaces b2 together form a square of the same size as surface of emergence.

I claim:

System composed of two optical square prisms, each adapted to deflect the ray passing through it by 90 and having a surface of entrance, a surface of emergence and two reflecting surfaces, all of which are perpen- -dicular to the same plane, the surfaces of lel to and facing the same Way as the cor- 1o responding surfaces of the other prism and the projection of two such parallel surfaces onto a plane parallel to them being a square.

ALBERT KONIG. Witnesses:

PAUL KRGER, FRITZ LANDER.

Copies o! this patent may be obtained for ve cents each, by addressing the Commissioner of Patents,

Washington, D. C. 

